Brazoria bridge similar to one in Minneapolis

Brazoria span only one similar to structure in Minnesota

RAD SALLEE, Copyright 2007 Houston Chronicle |
August 3, 2007

Rated least sufficient among Houston area bridges is the Brazos River bridge on FM 521, just outside Brazoria. Built in 1939, it is a rarity in the Houston area — a steel truss design that still carries traffic.

Photo By Courtesy of Alison Steele Mandadi

Rated least sufficient among Houston area bridges is the Brazos River bridge on FM 521, just outside Brazoria. Built in 1939, it is a rarity in the Houston area — a steel truss design that still carries traffic.

Photo By Courtesy of Alison Steele Mandadi

Rated least sufficient among Houston area bridges is the Brazos River bridge on FM 521, just outside Brazoria. Built in 1939, it is a rarity in the Houston area — a steel truss design that still carries traffic.

Photo By Smiley N. Pool/Chronicle

The Fred Hartman Bridge carries traffic from La Porte to Baytown on Texas 146 across the Houston Ship Channel. The U.S. government gives the span a 69 rating out of 100.

Fourteen of the more than 2,000 state-maintained bridges in Harris and adjoining counties are classified as "structurally deficient," but all are open to traffic and safe to drive, Texas Department of Transportation officials said Thursday.

And Jon Holt, assistant bridge engineer for the department's Houston District, said all the bridges are scheduled for repair or replacement.

Rated least sufficient among them is the Brazos River bridge on FM 521, just outside Brazoria. That aged span, built in 1939, is a rarity in the Houston area — a steel truss design that still carries traffic.

Its design is similar to that of the Interstate 35W bridge over the Mississippi River in Minneapolis that collapsed at rush hour Wednesday, killing at least four motorists and injuring 79.

Federal officials alerted states Thursday to immediately inspect all bridges similar to the Minneapolis span. The Brazoria bridge is the only one fitting that description in the Houston District, according to a Federal Highway Administration database that rates bridges from zero to 100 for structural sufficiency.

The Brazoria bridge is rated 22.5. There are plans to replace it while saving the existing structure as the centerpiece of a historical park. A rail bridge of similar design runs beside it.

TxDOT spokesman Mark Cross said Texans need not worry about a repeat of Wednesday's collapse, where the eight-lane Interstate 35W bridge buckled during the evening rush hour, sending dozens of cars more than 60 feet into the water.

That bridge, built in 1967, was undergoing repairs at the time. Federal officials had warned of its deficiencies since 1990, the Associated Press reported.

Classification misleading

Holt said a deficiency classification can be "kind of misleading because if they were really bad, we would shut them down and there would be emergency work going on."

For instance, among the 14 deficient bridges in the Houston TxDOT district, which also includes Galveston, Fort Bend, Brazoria, Waller and Montgomery counties, two are overpasses near downtown that were hit recently by trucks and are undergoing repair.

One is on the East Freeway over Wayside and the other on Waco over the East Freeway.

A third bridge on the list is on the westbound Katy Freeway frontage road near Studewood. It has a hole near a joint in its deck and will be replaced due to deterioration, Holt said.

Most Houston-area bridges use steel-reinforced concrete beams or steel box girders, instead of trusses, to support their decks, said Todd Helwig, a University of Texas structural engineer who taught for 12 years at the University of Houston.

Helwig said truss bridges typically are found in spans more than 300 feet long and reduce weight through the use of arches and other forms of bracing in place of solid blocks or sheets of material.

Truss bridges are not inherently more dangerous, but may need more frequent inspection as they age, he said.

"The members that make them up are usually under tension or compression and if you lose one of the primary members, you can lose the bridge," Helwig said.

Federal list longer

TxDOT's list includes only bridges that the department maintains, which includes those on farm to market roads, state highways and federal and interstate highways, but not most city streets, county roads, tollways or private roads.

The Federal Highway Administration list is much longer and classifies 25 bridges as structurally deficient in Harris County alone. Many are off the state system and lightly used.

For example, one spans Metzler Gully on Pine Cone Ranch Road in north Harris County and had a traffic count of 10 vehicles a day in 2005.

The most traveled on the FHWA list is the East Freeway at Wayside, with 188,000 vehicles a day.

The only major bridge in the Houston area with a low sufficiency score on the FHWA list in 2005 was the Galveston Causeway, rated in the low 30s. Today, that span is used for construction equipment only. Traffic now drives on a newly built causeway alongside it.

Trinity River bridge

Several other aging bridges in the area also are being replaced, including the Trinity River bridge on Interstate 10 East, built in 1955, and the Brazos River bridges on U.S. 59 South, built in 1971.

Statewide, the Associated Press reported, more than 2,100 Texas bridges were classified by the FHWA as structurally deficient, as was the Minneapolis bridge. Of these, 138 were part of the national highway system.

A 2006 TxDOT report said 4 percent of the state's approximately 50,000 bridges were structurally deficient, 77 percent were labeled good or better. Most of the rest were deemed functionally obsolete, meaning they were not designed to handle the current traffic demand.

TxDOT officials in Austin insisted Thursday that all the state's spans are safe. Texas ramped up its bridge repair efforts in 2001, setting a requirement that at least 80 percent of bridges be in good or better condition within a decade. As of September 2006, 77 percent of the state-maintained bridges were listed as good or better, a TxDOT study said.

Bridges are inspected at least every two years, Cross said, and those with critical issues are checked out more frequently.

Inspectors look for corrosion, deterioration and damage and check for cracks that signal fatigue, said Joseph Yura, a professor emeritus of engineering at the University of Texas at Austin who specializes in structural steel design.

Focus on road safety

State Sen. John Carona, a Dallas Republican who chairs the Senate Transportation Committee, said he hoped the new national focus on bridge safety persuades his colleagues to put more money into road construction and maintenance.

More than half of Texas' bridges were built before 1971, according to the Transportation Department. Of those, more than 9,000 were built before 1950. Many of those aging structures will need to be upgraded or replaced in the near future, said Carona, who wants to raise the motor fuels tax by 10 cents and tie it to inflation.

Chronicle reporter Chase Davis and the Associated Press contributed to this story.